Here is a useful tip that will keep you from chasing what you think is a gas leak that is etching the PolyBrush on your fabric belly.

I was having trouble finding the source of a persistent leak under my fuel tank.  The tank sits high behind the passengers, and about 18" above the fabric belly.  The smell of gasoline was strong, so that is what I assumed it was.  When I mopped it up, it was red, though.  Making the mistake of trusting an assumption, I figured it must be melting the red PolyBrush covering the belly's fabric.  I finally resorted to covering a large portion of the belly with old t-shirt fabric  after mopping up as much of the liquid as I could.  Left for a day, the fabric wicked up a few isolated spots of the old liquid, but nothing new.

The leak must have sealed itself. (Huh!?!)

OK.  Back to reality.  Tracking the stain as far uphill on the fabric as I could I noticed it was near a T in the brake line.  Wiped the fitting with a bit of the cloth, and sure enough got a red stain.  Slid the cloth underneath the fitting and pulled the brake lever.  Got a sputtering bubble of red liquid oozing from one side of the T. (Dang-it!!)  Grab a couple of wrenches, applied a 1/4 turn, and pull the brake lever again.  Hmm?  That seemed to be a LOT firmer than it has been.

The problem and resolution only takes a couple paragraphs, but I've been chasing this thing for a couple weeks.  I would suggest to builders:

1) Get rid of "cleanup rags" and anything else that will try to hold onto gasoline and gasoline smells after you're sure the tanks are sealed.  The rags being in the workshop kept the smell around and misled me to believe that there was still a leak.

2) Tie a piece of white cloth or paper napkin around all of your brake fittings before filling your brake system for the first time, then immediately apply the brakes until you get solid response.  Any leaks will show up as blaring red stop signs on the white cloth.